Our group recently reported that the mucin, Muc5ac, is induced in human airway cells via a COX-2 pathway (Molecular Pharmacology, 66:337, 2004). Muc5ac is one of the major mucins secreted in the stomach and lung. Muc5ac is believed to have roles in the gastric ulcer formation, and possible gastric cancer formation as well as influencing the lung?s susceptibility to infection or inflammation. To gain insight into the physiological roles of Muc5ac we are disrupting the Muc5ac gene in mice.